#geometry-and-trigonometry
1 messages · Page 280 of 1
the law of sines/law of cosines is suited for ALL triangles, not just right triangles
it's pretty useful to know
area segment = area of sector - area of triangle = $\frac{\pi*\theta}{360}*R^2 - \frac{R^2*sin(\theta)}{2}$
DanCastan:
Factor out $R^2$ and you just plug in the values
DanCastan:
yes
@upper karma the dark colored part from here? https://discordapp.com/channels/268882317391429632/326138757474680852/710570066198134864
also, is this a test?
@upper karma is this an exam?
i need some guidance
find circumcenter
Is there a formula for that? I haven't learnt what circumcenter is.
@lunar sand That question is wrong I believe
This was the circle made by @upper karma
Plotted
And it lies in the 1st quadrant so both of the co-ordinates of the centre have to be positive but they arent
I also tried the question in a different way
By assuming every option as the centre and calculating the radius but I never got the same radius for every distance in any option
well, I'll just get a few more opinions on the question before deciding that it's an impossible question.
ah, yeah. I didn't mean it that way.
Do you want to solve it regardless the options?
If you want to do it that way then you can take the coordinates of the centre as (x, y)
@upper karma did you also get the same result?
@upper karma rounded to the nearest tenth would be 13.9
could someone help i cant fine how to do this i dont need the answer just a formula i can use or a link to a khan academy vid on this
^this was question 24
Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.
Let’s

@shell merlin Use Intersecting Chord Theorem
@shell merlin how long is the radius?
and would you say it's the same as this?
@shell merlin and can you figure out half of AB?
hint: ||Pythagora||
@upper karma did you go through those videos?
What about Intersecting Chords Theorem 😭
🙂
😳
thx im good @upper karma
epic 
@upper karma which one?
which one from questions 25-32?
@upper karma so you need help with all of them except 28 and 31
@upper karma what can you tell me about angle BAX?
it's an inscribed angle
how about now?
what can you tell me about that angle now?
what's the measure of angle BAX?
yes
how long is arc EX?
remember, the whole circle is 360 degrees
yes
and are there any angles we could use with this arc?
180 + 100 + 80 = 360
sure
yep
if that's the new diameter, what is the measurement of angle ABC?
so that takes care of questions 25 and 32
This geometry video tutorial provides a basic introduction into circle theorems. It contains plenty of examples and practice problems.
Here is a list of topics:
- If a radius is perpendicular to a chord, it bisects the chord into two congruent segments. The point of conta...
Circle theorems are pretty awesome
Ngl
Oh
Learn to love them
did you see the above video?
good
This geometry video tutorial provides a basic introduction into circle theorems. It contains plenty of examples and practice problems.
Here is a list of topics:
- If a radius is perpendicular to a chord, it bisects the chord into two congruent segments. The point of conta...
click the video
it has a timestamp
yes
the guy even explains what an inscribed angle is
(all the vertices of the triangle are on the circumference of the circle)
half, yes
so that would be question 26
Would anyone be willing to help me?
@agile tree I'll be with you in a sec
Thanks spider
Im still here waiting spider just lmk when u can help
Dm me @upper karma
public is better
No, on #prealg-and-algebra
so other people can pitch in and correct
Yeah
I said it bc of bots lol
But ok
anyone know about coterminal angles
@upper karma you got them all
good job
I was about to ask you how long is arc AD
but you got it right
well, what is the measure of this angle?
?
ok
yes
it's an inscribed angle
so you know all angles from a triangle add up to 180 degrees?
and if that angle is 90... and the entire equation needs to equal 180...
they other two add up to 90
they're not necessarily both 45 degrees
you didn't watch the above video 😦
you would add those expressions + 90 = 180
yes
(1/2)x + (1/3)x + 5 + 90 = 180
solve for x
,w (1/2)x + (1/3)x + 5 + 90 = 180
how do you find the quadrant of a negative angle?
@thorn holly google "unit circle quadrants"
Thales theorem and angle sum of a triangle should help
@upper karma https://youtu.be/XWqP9T7-HXM?t=907
This geometry video tutorial provides a basic introduction into tangent lines and secant lines as it relates to circles. A secant line touches a circle at two points. A tangent line touches a circle at exactly one point. The radius of a circle and a tangent line are always ...
sure, no problem
I'm off to bed
@prime barn post your question if it's related to trig
maybe someone can help
well its a weirder question where you need custom equations
if it's not related to trigonometry/geometry, maybe post in one of the #help-2 [greek_letter] channels
In order to find the height of a tree, would it be good enough to get a protractor to measure from the ground to the top of the tree? Also, I will measure the distance from the base of the tree to where i'm standing. I can't afford expensive gizmos. If someone thinks there is a better way, please suggest ideas. Thanks.
@shell raft you don't necessarily need to be on the ground... you can put it on top of a vertical stick that has a fixed height (e.g. 1 m)
once you have the angle you need to know the distance from you to the tree
and then just take an angle measurement from you to the top of the tree
then, because you have 2 angles and a distance (one angle you measured, the other is 90 degrees), you can easily get the height of the tree
thank you dspider.
thank you.
the answer is correct.
is the bottom not included?
Also not to be that guy but if you sub pi as 3.14 the answer is 18.84 not 18.85 lol
sorry, that is my fault. i didn't use 3.14 and i rounded at the end so i assumed roku did that as well.
Could someone possibly assist me with this?
Find a Ferriswheel. State name and location. Find length of time for a rotation and the diameter. If it does not mention where people board assume it is at ground level. Create a table giving height based on time have the correct units. Find midline amplitude and period and from this info get formula for the function that gives you height.
I'm using the High Roller which is 550ft tall with a diameter of 520ft and has a total rotation time of 30 minutes
@kind glen midline is 30+radius, amp = radius, 2pi/30 = k, or the stretch/compression. cos starts at the top so you have to do k(x-half the period) or just put a negative infront of a, where a is the amplitude in acos(k(x-d))+c
what's giving you trouble here
find the area of a cross section
do you know the formula for triangle's area?
so it would 18 yd squared
.
oh
21 yd squared?
27 yd ^2
27?
then area is
yes 27
then you multipliy this are by the width of base of prism
which is 8 yd
and get 27*8=216
right
so the volume is 216 yd^3
because
unit of length times unit of height times unit of width us yd^3
yd times yd times yd is yd^3
ah okay i remember that
okay
im going to do this one
lets see if i can do it right
175 yd^3
yep
finally
someone helps me and simplifies it
thank you so much
ill finish this up and
i have more mabye
if you have time
don't feel obligated
thank u
you are free to write in private message if you need or to ask someone another, i think someone would anyway help you
no worries
formula for a circle area is A=pi*r^2. what you ahve there is a semicircle, which is half a circle
so it would be half of that formula
the diagram didn't give you the specific radius.
it gave you something else to figure out the radius. Do you notice what that might be?
yes. can you use one of the values from that rectangle to figure out the radius?
notice these two sides are the same length
since its a rectangle
i.e theyre both 18 ft
does that make sense to you?
do you see how to get the radius from there?
i cant seem to find
my formulas
mind helping me with this one
then ill try working on my own
so whats the forrmula
formulas you need here are area of rectangle=lw where l is length and w width, and area of a semicircle=(pi*r^2)/2
how about now? do you see the radius now?
9?
of course
ahhhhh
right so,
3.14 (9)^2/2
28.26
is what i have here
- the area of the rectangle
,w (3.14* ((9))^2)/2
Area?
ft^3 would be for volume
right
ok
squared
your right
you're*
(you + are = you're)
oh my answer
was way off
and 74.26 is wrong
oops
well, no
now
it's not letting go back
its on this practice website
this shit is so hard for me
for whatever reason
that doesnt sound right
would be
uhh danny. your answer is close but it is not right. did you use 3.14 for pi?
,calc (1/2)3.146^2
Result:
56.52
right
how did you round it?
your answer was 56.549. did you do (1/2)*3.14 *6^2 to get that?
did you use a calculator? it should be 56.52
i messed up the pi
somehow
thats probably it then
so now we wanna get the area of the triangle right?
yes
do you know the formula for that?
base and height
ok so base * height/2 yeah
yeah
can you recognise what those are?
yes
so they are ?
base would be 18.84
how did you get that?
how did you get that...
okay
b is the same as the diameter of the circle, right?
yes
if the radius is 6, the diameter is _________?
?
...
thats correct but let me explain why first....
remember the diameter is twice the radius
Because a radius is from center to circumference
3
And a diameter connects 2 end points of the circumference
i mean
And passes through the middle
diameter is twice the radius
okay
72
/2
/2 = 36
yup
okay
now whats the shaded area, in terms of the area of the semicircle and the area of the triangle?
mm the shaded area is the area of the semicircle minus the area of the triangle right?
correct
and the shaded area is the semicircles area minus the triangles area
mm
so whats that?
,calc 56.52-36
Result:
20.52
ok
you lost a 4 somewhere
im sorry..
its 3:15 am
im having troubles staying awake
but i need to finish this
so we have 20.52
after subtracting
so thats your answer?
20.52 ft ^2 is my final answer
sounds good
Are there any elliptic theorems in angles just like with circle theorems but with ellipses?
well, an ellipse is just a circle with one of its axis slightly dilated or stretched
I think the same theorems for circles should apply, as long as you account for that stretch/squish ratio
well, an ellipse is just a circle with one of its axis slightly dilated or stretched
more correctly is to say that a circle is an ellipse with equal major and minor axes
@azure reef and an ellipse is a circle with one of its axis slightly dilated or stretched is correct too
Consider a transformation called orthogonal affinity
Let its direction be parallel to one of the axis of the ellipse
And its ratio be the ratio of the lengths of the axis
Then it transforms the ellipse to a circle
Both are correct
You van transform a circle toban ellipse in this transformation
And an ellipse to a circle too
sure, but i mean that from the point of view of analytic geometry ellipse is more general case
You can see a circle as an ellipse but with focii the same point, the center of the circle
Yes sure
Ellipse: x^2/a^2+y^2/b^2=1
Circle x^2/a^2+y^2/a^2=1
The ellipse is more general yes I see what you mean
anyway, it is just terminology, one can use this terms interchangeably except for specific problems
Yes
We can go from circle and the generalize to ellipse, analytically or geometrically
Or we can go from the general case, ellipse, to the particular case, circle
what does it mean to find the equation of a line such that the composition Rx-axis ∘ Rl = R0,90?
I understand Rx-axis would be reflecting the line upon the x-axis
what does Rl and R0,90 mean?
if im trying to find the area of parallelogram and got the height, but there are two different bases.. which one do I use?
let me send a pic
Ok
This is not a parallelogram
The shaded region is limited by a quadrilateral that is not a parallelogram
so what is the formula to shade it?
the textbook lesson was saying the formula was a=bh
For a parallelogram yes
well im suppose to find the area of the shaded polygon, so do i d 16*10?
No
so how can i do it
You can see the shaded region as a parallelogram and a triangle next to each other
So the area of the shaded region is the sum of the area of that parallelogram and the area of that triangle
the triangle on the right?
You know that for a prallelogram the area is given by A=base×height and for a triangle the area is A=base×height/2
Apply this to this figure
No not the triangle on the right for sure, because it's not shaded
The triangle on the left
how can i find the height for the triangle on the left?
It is the height given !
For the parallelogram and the triangle
h=10m for both the parallelogram and the triangle
ok so the area of the parallelogram is 110
and the area of the triangle is 25?
so do we add it to find the area of the shaded?
True
Do you know Pythagoras' theorem?
yes
Use it here
ohh
To find the height that is common for eachvof the two triangles and the parallelogram
You should get 24 I guess
wait i used the 10+x=26
This is not Pythagoras' theorem
but arent they already squared?
i think i made a mistake in the 2nd triangkle
its a trapezoid.-.
yoh
anyone here able to help me with a problem i got
i got no clue how to work the problem
you can find "a" by pythagoras
then use pi * a^2 to find the area
"Given that the tent is a spherical radius of..."
I'm sorry, what?
the tent is a spherical radius?
Find a using r^2-(r-h)^2=a^2
@upper karma AO is also a radius of the circle
the length of CO can be obtained from r - h
and then apply pythag to get a
can someone help me
@dense sky what do you know about tangents of a circle
co, ob?
so what is the length of CD
20
capitals, the notation implies the length of those line segments
and the length of NW
20?
no...
so CZ is equal to ZN right
yeah
so ZN= to what?
20? ;-;
the image is basically a cross section of the middle of the dome
i dunno what NW is..
dude
omg
@upper karma fail what?
is this a test?
if i miss 1 question on this i fail the semester
no its not a test
we have these learning progress checks every week, i got mono and recently recovered so ive had to do 1 months worth of work this week
and im not able to get help from teachers for atleast 2 days and by then it will be over
and the cross section of that dome would be part of a bigger circle
since they nicely provided the diagram for you, you can ignore most of the text and just use that
i legit never got a video tutorial on these
ive had to search everything up and some shit idek what to search up
so is the r the 14.1 ft
wtf is it then
...
got my things mixed up.
Do i do 8x+4=9x-5 and go from there?
then how am i suppose to find co
not sure why but this is confusing me
yeah
^
any of the #help-2 [greek letter]
wait
so its =\sqrt(14.1^(2)-6.1^(2))
that didnt want to show up pretty
@upper karma so just put my problem in any of those channels?
yes
if it's free unocuppied
@upper karma so what's the length of OC?
the same as ac?
look at the image I posted above
wait
the red question mark
yeah
do you see it?
OC + CA = AO = r
oh
alr
8.8
...
read that num wrong
ITS Hard to read
it is, isn't it?
..
8
look at the problem's requirements
yes
ok
so you've got 14.1 - 6.1 = 8
good
now do you see where Pythagoras' theorem could be applied?
yh
a = ?
11.61077086
,w a^2 + 8^2 = 14.1^2
this shit is hard without knowing how to do it, any of the terms, and no fucking teacher
ok
ah shit
the next one is on the same tent
fuck this tent
"To the nearest foot how tall could the tent be if a group of campers needed 127.7π square feet of ground space in a tent with a spherical radius of 16.9-feet?"
if you round it to the nearest hundred, it's 11.61 ft
yeah i put that
sorry, but could you help me on this one
ok, so the area of this new hemisphere (?) is 127.7 pi ft^2, with a radius of 16.9
why do you think it's the same tent?
no, same image type shit
post it
let's see
ok, so square feet is the area
area of a circle
do you know the formula?
(google it)
of the area of a circle?
yes
yeah
wait
or maybe you don't need it
do i need to find out the radius through that
just take the square root of 127.7
and i would get the radius
but they already give you the radius?
or do they give you the radius of the sphere?
radius of the sphere
spherical radius
yeah
it's the sphere
carry on
you're doing great
so you have the area for the ground floor (which is a circle)
did you google the formula?
yeah
oh
did i google it?
no
what's the formula for the area of a circle?
i had to use that formula in a diff problem earlier
pie r squared
pi
good
but its asking about height?/
so you have pi r^2 = 127.7pi
solve for r
we'll get to the height in a moment
11.30044246
right?
i mean i understand how to get the radius i just dont know what that has to do with the question
yep
ok, so the radius of the ground floor (which is a circle), is 11.3
using Pythagoras' theorem, can you solve the red question mark?
um
no
(which kinda looks more like a fat exclamation mark, lol)
you would need the height in order to do that
how about now?
oh
im dumb
already got 2
🙂
it's 2?
you only need 2 sides for it...
thats what im talking about
where did you get "2" from?
the a and r
you need 2 sides for Pythagorean theorem?????
uh, yes?
of course
bruh
what do you mean ofc, you asked where i got 2 from
i was talking about there already being 2 sides
...
,w x^2 + 11.3^2 = 16.9^2
yeah
got that
actually
not rlly
i got 12.56622458
I thought you meant you calculated it... ok, whatever
so OC = 12.6
yeah
... I tried to solve this problem and it had 2 solutions
okay whats next???
h = ?
4.33377542
rounded to the nearest tenth?
its to the nearest foot
rounded to the nearest foot, actually
yeah
yh
4
4, yes
there you go
congratulations
not nearest
ree thats so dumb
you'd need to round up
no
otherwise there wont be enough area
the answer could be 29, but the tent would be weird
5 would be the nearest foot
its not about the real world though
I would still put it down as 4.3
im doing 4
16.9 - 12.6 = 4.3
it will tell me if its wrong and if it is i can just do the same thing with different numbers
4 does make more sense (to me at least)
oh, cool
there you go then
same since its not a real world application
isn't 29 technically still correct?
let us know which value it takes
well i still got 1 more
ima try to work on it myself rn
ok
good
Is anyone able to help me with my question in question room?
which question room @upper karma
lol
Anyone wanna try a question i made myself?
no im still braindead
closing in on 3 days no sleep
go sleep
no
i cant
i need to finish my classes
im barely doing classwork lol since they're not graded .-.
they are for me
i need atleast 3/4 to pass the semester on everything
i had mono for a month so when i got back to healthy, i ended up having 150 missing assignments
started on Tuesday and I'm almost done with them all
no
oof
and i didnt get any note videos
so ive had to do this all without learning the vocab or material
that really unfair
did ur parents email the teacher?
ive emailed them all myself with a doctors note
apparently i couldn't get absent time off since its online school and not going to the actual school.
that really got to suck
eh
i have a friend that helped do some of my essays
she fucking amazing at them. shes like at stanford right now studying ChE
last thing she sent me
" working in a bioengineering research lab with a master's student. she had just begun her thesis so i was able to work with her on her research and later become published. we worked with mesenchymal stem cells in hydrogel scaffolds and their abilities to speed up wound healing. the experiments were very time-sensitive so i found myself in the lab, often by myself, at weird hours in the evening when everyone else had left. that was by far my favorite part of senior year."
yeah im in highschool rn
oof
eh
i feel very unproductive
im graduating early
lol its alr
sometimes you need to be unproductive to give you that motivation to be productive.
ree
ive been trying out this thing with ego depletion
like I've been trying to make myself believe I don't need breaks and so far I'm 18 hours in without one.
@upper karma what have you tried
perpendicular slope of a/b = -b/a
ok someone just give the answer 😌
@full ruin hell no, we dont do that here
LMAOO
ok teach me them
then i’ll learn
i’m a fast learner
is it the third one @upper karma
i tried plugging in the points they gave me cause i had nothing else to try
you can use POINT SLOPE FORM along with the perpendicular slope
if you recall that slope is:
you can rewrite it:
ooo yes i understand this one
you can replace the m with your slope and the x1,y1 with your given points
then turn it into a nice looking [y=mx + b] equation
the other option would have been looking at those 4 answers, determining which of them used the correct perpendicular slope. (the top two choices)
and then plugging the point in and seeing if it satisfies the equation (is the point in the line? )
@lament harness Were you planning on asking a question or just posting the picture as decoration?
why would I post a picture for decoration??
oh yea I forgot the question
I need help on c)
What help do you need? What have you tried? Were you able to do parts a) and b) successfully?
Well, I assume that you have:
$\sin^2(C) = \sin^2(A)+\sin^2(B)+2\sin(A)\sin(B)$
$\cos^2(C) = \cos^2(A) + \cos^2(B) + 2\cos(A)\cos(B)$
Abhijeet Vats:
Yes?
yes
So:
$\sin^2(C) + \cos^2(C) = \sin^2(A) + \cos^2(A) + \sin^2(B) + \cos^2(B) + 2\sin(A)\sin(B) + 2\cos(A)\cos(B)$
Yes?
Abhijeet Vats:
I just added the both of them
alright
So:
$1 = 1 + 1 +2[\cos(A)\cos(B) + \sin(A)\sin(B)]$
Abhijeet Vats:
Can you use that to determine A-B
You're welcome.
Do trig identities still apply to inverse trig functions?
no
ok, thank you
well, try applying one
sin(theta) + cos(theta) = 1
...for which their inverse would be:
sin^-1(theta) + cos^-1(theta) = 1
regardless of angle, they won't ever equal 1
sin(theta) + cos(theta) = 1
wtf
wtf
@acoustic jungle well, it’s a conditionally true equation, just not an identity
Also, while simply replacing the trig function in the identity with its inverse function is likely what saif was meaning, that’s not what the inverse of a trig identity would be
@candid terrace Hint, angle TAB and angle TCB are right angles. You have 2 sides of the triangles, what's stopping you from getting the 3rd?
Yea they are right angles because the angle between a tangent and radius is 90
That’s a theorem
Ye?
I’m still having trouble understanding what I should be doing
I’m finding the perimeter
You know the radius right?
So you know that the two sides inside the circle are both 8.
8
What you need to do is to find line CB and AB.
I feel so stupid, I was staring right at it
If you're stuck, just read the question then ask yourself: "What does this information tell me?"
They don't tell you that certain lines are tangent for the hell of it.
But hold on
Ye?
You need to find it yourself.
Imma look up circle theorems
Nonono.
Stay here.
You have two right triangles that are shaped like this.
Use the Pythagorean theorem to find the side.
@candid terrace
17 is that center line.
Pretty awesome
Lol yes.
Ok
It’s 15
🥳
Ok
All seriousness
This assignment is due at 12:00
I have 30 minutes left
But
It’s says the perimeter of ABCT
@upper karma
So is the answer 46?
Since I’m not counting the hypotenuse
Ya ik
ABCT
Ok
Please stay and help with the rest
This assignment is due in half an hour
@candid terrace This problem is the same as the last one.
Except you have to draw some extra lines.
Draw a line from T to J.
And then you have an exact replica of the last problem.
Two right triangles next to each other and you have a shit ton of sides to go off of.
Mhm.
Jp 8
Yes
JT 12?
No
Then what is it?😥
You probably did your arithmetic wrong
I can’t find the length of the hypothenuse
It’s 13
Yea
But that’s the answer
?
Yep
How do I find that
By drawing line JT, 2 right triangles are formed